Are you in a rush to get the box into production?
If not, try it and see how it goes.
You write:
"it looks like it only supports windows so that makes me wonder..."
Not to worry windows 2003 server is just another flavor of good old crappy windows so your on board adaptec controller should work just fine.
If the on board controller does not work, you can always do a "software" mirror in windows 2003 server.
Here is a link to MS with instructions on how to do it:
http://support.microsoft.com/kb/323432
Good luck with it
